Magnetic snap switch



Feb. 19, 1957 D. PETERS 2,782,278

MAGNETIC SNAP SWITCH Filed April 2'7, 1954 I 26 l8 I 24 I i9 0 A L 32;-

23 J 6J8 as INVENTOR MAX 0. PETERS BY j ATTORNEY United States PatentMAGNETIC SNAP SWITCH Max D. Peters, Minneapolis, Minn., assignor toMinneapolis-Houeywell Regulator Company, Minneapolis, Minn., acorporation of Delaware Application April 27, 1954, Serial No. 425,87113 Claims. (31. 200-67) This invention relates to switches and moreparticularly to magnetic snap switches.

One embodiment of my invention has as the basic elements of the switch,three contacts, opposed magnets, and a moving element. supported at itscenter of gravity by a thin stainless steel wire. I depend on thetorsion of the wire to hold the moving contact against the normallyclosed contact.

The magnets, due to their negative spring rate efie'ct on the armature,establish an unstable system which provides snap action. By properlyselecting and adjusting the magnets, a switch can be designed to givealmost any desired characteristic. In a sensitive switch for instrumentuse, the work input should be minimized. To produce rapid armatureacceleration and fast contact break, the magnet force should droprapidly as the armature moves away from it. This effect is produced byusing small magnets and by having the armature approach them veryclosely. As the air gap of a magnet and armature is decreased, the rateof change of force with distance becomes increasingly great.

My invention provides a switch that has a low force differential and ishighly resistant to vibration eliects.

My invention can be utilized wherever a snap switch with low forcedifferential characteristics is desired.

Therefore an object of my invention is to provide a switch of the typedescribed that is simple in construction, light in weight and reliablein operation.

Another object of my invention is to provide a snap switch with a lowforce differential.

Yet another object of my invention is to provide a snap switch that ishighly resistant to vibration effects.

Other objects and advantages of my invention will in part be obvious andin part be described when the following specification is read inconjunction with the drawings in which:

Figure 1 is a sectional elevation of the switch, and

Figure 2 is a fragmentary plane view of the U-shaped member, torsionwire, and lever arm.

Referring now to the drawings, a U-shaped member 11 of electricalconducting and mechanically resilient material is attached to a casing12 or dielectric material by screws 13 and nuts 14. U-sha'pe'd member 11is within the inner chamber 15 of casing 12. A torsion wire 18 passesthrough holes 26 and 21 in U-shaped member 11 and is attached by asoldering operation thereto. U"- shaped member 11 has a normal shape toapply a tensile force to torsion wire 18. Brackets 23 and 24 areattached to U-shaped member 11 at 25 and 2h. Brackets 23 and 24 haveslots of slightly greater width than the diameter of wire 13. Thetorsion wire 18 passes through the slots in brackets 23 and 24 but doesnot engage them in normal switch operation. The guide brackets 23 and 24offer no restriction to a twisting movement of torsion wire I8 but dotend to restrict any other movement. These guide brackets reduce anyv'ibr ation efiect's,

Lever arm 30 of electrical conducting material is attached to torsionwire 18 midway between the legs of U-shaped member 11. Torsion wire 18is weaved through holes 31 and 32 in lever arm 30 and attached to lever30 by a soldering operation. This point of attachment is at theapproximate center of gravity of lever 30 and is the fulcrum of lever30. Movable contacts 34 and 35 are carried on the right hand end oflever 30. A pigtail connector 37 interconnects lever 30 and U-shapedmember 11. Stationary contacts 39 and 40 are carried on the inner endsof members 42 and 43 of electrical conducting material screw mounted incasing 12.

Permanent magnets 45 and 46 are carried on the inner ends of members 48and 49. Members 48 and 49 are screw mounted in casing 1-2. The left handend of lever 30 acts as an armature 5i) and cooperates with magnets 45and 46 to give snap action to any movement of lever 30.

An actuator 53 is movably mounted in a bushing 54 screw mounted incasing 12. Actuator 53 has an abut ment 56 that cooperates with the topof bushing 54 to limit the extent of movement downward of actuator 53 inbushing 54. There is a snap ring 58 on the lower portion of actuator 53that cooperates with the bottom of bushing 54 to limit the extent ofupward movement of actuator 53 in bushing 54. A compression spring 60 isin between actuator 53 and lever 30. There is a socket 61in the bottomof actuator 53 to receive one end of spring 6% and a depression 62 inlever 30 to receive the other end of spring 6%. Depression 62 in lever30 is displaced from the fulcrum of lever 30.

In this embodiment of my invention the switch is shown with a normalposition of movable contact 34 engaging stationary contact 39. Lever 30is biased to this position by a twisting moment in torsion wire 18. Themagnetic influence of magnet 46 on. the armature portion 50 of lever 39helps maintain constant contact pressure between contacts 34 and 39. Aforce on. actuator 53 is stored in compression spring 60 until thatforce becomes suilicient to overcome the influence of magnet 46 and thetwisting moment in torsion wire 18. At this point lever 30 snaps to theposition where contacts 35 and 40 are engaged. This snap action is due"to the rapidly decreasing effect of magnet 46 andthe rapidly increasingeffect of magnet 45 on armature S0, and also the stored force in spring60. Upon release of this force on actuator 53 the clockwise twistingmoment in the torsion wire 18 is greater than the influenceof magnet '45on armature 51 which causes contacts 35 and 40 to break and contacts 34and 3% to make. The breakingv of contacts 35 and 40 is a snap action dueto the rapidly decreasing effect of magnet 45 and the rapidly increasingefiect of magnet 45. Cover plate 54 is attached to casing 12 by screws65.

By adjusting the position of member 42 in the casing the normal positionof the lever can be varied to get the desired amount of torsion in 'wireis. The relative spacing of contact carrying members 42 and 43 as wellas the relative spacing of magnets 45 and 46 can be adjusted to arriveat the desired differential. Therefore my switch has many and varieduseful applications.

Various changes obviously could be made in the described embodiment ofthe invention without departing from the basic inventive concept. Thescope of the invention is to be limited only by the appended claims.

I claim as my invention:

1. A snap-acting switch including in combination a casing with an innerchamber, a U-shaped member within said chamber attached to said casing,a torsion wire suspended across said U-shaped member near the ends ofthe legs of said 'U-shaped member, said 'U-shaped member exerting a-tensile force on said torsion wire, a lever arm mounted near its centerat the center of said torsion wire, the fulcrum of said lever beingestablished by said torsion wire, movable contacts mounted on oppositesides of a first end of said lever, stationary contacts mounted in saidcasing and disposed on opposite sides of said first end of said lever tocooperate with said movable contacts, said torsion wire biasing saidlever to a normal position in engagement with one of said stationarycontacts, magnets mounted in said casing on opposite sides of the secondend of said lever and in spaced relation thereto, said second end ofsaid lever acting as an armature, said magnets cooperating with saidsecond end of said lever to provide snap action of said lever, anactuator movable in said casing, a compression spring between said leverand said actuator to apply a force to said lever on a line displacedfrom said fulcrum, suificient force on said actuator causing said leverto snap from said normal position to engage the other stationarycontact.

2. A snap-acting switch including in combination, a frame, a U-shapedmember attached to said frame, a torsion wire suspended across saidU-shaped member near the ends of the legs of said U-shaped member, saidU-shaped member exerting a tensile force on said torsion wire, a leverarm mounted near its center at the center of said torsion wire, thefulcrum of said lever being established by said torsion wire, guidesbetween said lever and said U-shaped member attached to said U-shapedmember restricting other than a twisting movement of said torsion wire,movable contacts mounted on opposite sides of a first end of said lever,stationary contacts mounted on said frame and disposed on opposite sidesof said first end of said lever to cooperate with said movable contacts,said torsion wire biasing said lever to a normal position in engagementwith one of said stationary contacts, magnets mounted on said frame onopposite sides of the second end of said lever and in spaced relationthereto, said second end of said lever acting as an armature, saidmagnets cooperating with said second end of said lever to provide snapaction on said lever, an actuator movable in said frame, a compressionspring between said lever and said actuator to apply a force to saidlever on a line displaced from said fulcrum, sufficient force on saidactuator causing said lever to snap from said normal position to engagethe other stationary contact.

3. A snap-acting switch including in combination, a casing with an innerchamber, a torsion wire suspended across said chamber, a means forattaching said torsion wire to said casing and exerting a tensile forceon said torsion wire, a lever arm mounted near its center at the centerof said torsion wire, the fulcrum of said lever being established bysaid torsion wire, movable contacts mounted on opposite sides of a firstend of said lever, stationary contacts mounted in said casing anddisposed on opposite sides of said first end of said lever to cooperatewith said movable contacts, said torsion wire biasing said lever to anormal position in engagement with one of said stationary contacts,magnets mounted in said casing on opposite sides of a second end of saidlever acting as an armature, said magnets cooperating with said secondend of said lever to provide snap action of said lever, an actuatormovable in said casing, a compression spring between said lever and saidactuator to apply a force to said lever on a line displaced from saidfulcrum, sufficient force on said actuator causing said lever to snapfrom said normal position to engage the other stationary contact.

4. A snap acting mechanism including in combination a frame, a torsionwire suspended in said frame, a lever arm mounted near the center ofsaid torsion wire, the fulcrum of said lever being established by saidtorsion wire, stops mounted in said frame and disposed on opposite sidesof a first end of said lever to cooperate with said lever, said torsionwire biasing said lever to a normal position in engagement with one ofsaid stops, magnetic means mounted in said frame with opposing poles onopposite sides of .a second end of said lever and in spaced relationthereto, said second end of said lever acting as an armature, saidmagnetic means cooperating with said second end of said lever to providesnap action in said lever, an actuator movable in said frame, saidactuator engaging said lever on a line displaced from said fulcrum,sufficient force on said actuator causing said lever to snap from saidnormal position to engage the other stop.

5. A snap acting mechanism including in combination, a frame, a torsionwire suspended across said frame, means of attaching said torsion wireto said frame, a lever arm mounted at its center of gravity at thecenter of said torsion wire, the fulcrum of said lever being establishedby said torsion wire, stops mounted on said frame and disposed onopposite sides of said first end of said lever to cooperate with saidfirst end of said lever, said stops being adjustable in position, anormal position of said lever determined by one of said adjustablestops, magnetic means mounted on said frame with opposing poles onopposite sides of the second end of said lever in spaced relationthereto, said second end of said levcr acting as an armature, saidmagnetic means cooperating with said second end of said lever to providesnap action of said lever, actuating means movable in said frame, saidactuating means including spring means adapted to apply forces to saidlever on a line displaced from said fulcrum, sufi'icient force on saidactuating means causing said lever to snap from said normal position toengage the other of the stops.

6. A snap acting switch including in combination a frame, a torsion wiresuspended in said frame, a means of attaching said torsion wire to saidframe exerting a tensile force on said torsion wire, a lever arm mountednear its center at the center of said torsion wire, the fulcrum of saidlever being established by said torsion wire, a movable contact mountedon one side of one end of said lever, a stationary contact mounted insaid frame disposed to cooperate with said movable contact, a magnetmounted in said frame in spaced relation to a second end of said lever,said second end of said lever acting as an armature, said magnetcooperating with said second end of said lever to provide snap action ofsaid lever, a normal position of said lever with said movable contact inengagement with said stationary contact and said magnet cooperating withsaid armature, an actuator movable in said frame, a compression springbetween said lever and said actuator to apply a force to said lever on aline displaced from said fulcrum, sufficient force on said actuatorcausing said lever to snap from said normal position away from saidstationary contact.

7. A snap acting switch including in combination a frame, a torsionmember mounted in said frame, a lever arm mounted near its center at thecenter of said torsion member, a contact on the first end of said lever,a stationary contact mounted in said frame to cooperate with saidmovable contact, magnetic means mounted in said frame in spaced relationto a second end of said lever, said second end of said lever acting asan armature, said magnetic means cooperating with said armature toprovide snap action of said contacts, a resilient actuator movable insaid frame, said actuator engaging said lever upon a force appliedthereto causing said lever to move With snap action.

8. A switch including in combination a frame, a torsion member mountedin said frame, a lever arm mounted near its center at the center of saidtorsion member and supported thereby, a contact on the first end of saidlever, a stationary contact mounted in said frame to cooperate with saidmovable contact, magnetic means mounted on said frame in spaced relationto a second end of said lever, said second end of said lever acting asan armature.

9. snap acting switch including in combination a.

casing with an inner chamber, torsion wire suspended across saidchamber, means for attaching said torsion wire to said casing, a leverarm mounted at its center of gravity at the center of said torsion wire,the fulcrum of said lever being established by said torsion wire,movable contacts mounted on opposite sides of a first end of said lever,stationary contacts mounted in said casing disposed on opposite sides ofsaid first end of said lever to cooperate with said movable contacts,each of said stationary contacts being adjustable in said casing, saidtorsion wire biasing said lever to a normal position in engagement withone of said stationary contacts, magnets mounted in said casing onopposite sides of the second end of said lever and in spaced relationthereto, each of said magnets being adjustable in said casing, saidsecond end of said lever acting as an armature, said magnets cooperatingwith said second end of said lever to provide snap action of said lever,an actuator movable in said casing, a compression spring between saidlever and said actuator to apply a force to said lever on a linedisplaced from said fulcrum, sufficient force on said actuator causingsaid lever to snap from said normal position to engage the otherstationary contact.

10. A snap acting mechanism including in combination, a casing with aninner chamber, a U-shaped member within said chamber attached to saidcasing, a torsion wire suspended across said U-shaped member near theends of the legs of said U-shaped member, said U-shaped member exertinga tensile force on said torsion wire, a lever arm mounted at its centerof gravity at the center of said torsion wire, guides between said leverand said U-shaped member attached to said U-shaped member forrestricting other than a twisting movement of said torsion wire, thefulcrum of said lever being established by said torsion wire, stopsmounted on said casing and disposed in opposite sides of a first end ofsaid lever to cooperate with said first end of said lever, said torsionwire biasing said lever to a normal position in engagement with one ofsaid stops, a magnetic means mounted in said casing with opposing poleson opposite sides of the second end of said lever and in spaced relationthereto, said second end of said lever acting as an armature, saidmagnetic means cooperating with said second end of said lever to providesnap action of said lever, an actuator movable in said casing, acompression spring between said lever and said actuator to apply a forceto said lever on a line displaced from said fulcrum, sufiicient force onsaid actuator causing said lever to snap from said normal position toengage the other stop.

11. A snap acting switch including in combination a frame, a U-shapedmember attached to said frame a torsion member suspended across saidU-shaped member near the ends of the legs of said U-shaped member, saidU-shaped member exerting a tensile force on said torsion member, a leverarm mounted near its center at the center of said torsion member, thefulcrum of said lever being established by said torsion member, movablecontacts mounted on opposite sides on the first end of said lever,stationary contacts mounted in said frame and disposed on opposite sidesof said first end of said lever cooperate with said movable contacts,said torsion member biasing said lever to a normal position inengagement with one of said stationary contacts, magnets mounted in saidframe on opposite sides on the second end of said lever in spacedrelation thereto, said second end of said lever acting as an armature,said magnets cooperating with said second end of said lever to providesnap action of said lever, an actuator movable in said casing, acompression spring between said lever and said actuator to apply a forceto said lever on a line displaced from said fulcrum, sutiicient force onsaid actuator causing said lever to snap from said normal position toengage the other stationary contact.

12. A snap acting switch including in combination a frame, a U-shapedmember mounted in said frame, a torsion member suspended across saidU-shaped member near the ends of the legs of said U-shaped member, saidU-shaped member exerting a tensile force on said torsion member, a leverarm mounted near its center at the center of said torsion member, thefulcrum of said lever being established by said torsion member, stopsbetween said lever and said U-shaped member attached to said U-shapedmember for restricting other than a twisting movement of said torsionmember, movable contacts mounted on opposite sides of the first end ofsaid lever, stationary contacts mounted in said frame and disposed onopposite sides of said first end of said lever cooperate with saidmovable contacts, magnets mounted in said frame on opposite sides of thesecond end of said lever in spaced relation thereto, said second end ofsaid lever acting as an armature, said magnets cooperating with saidsecond end of said lever to provide snap action of said lever, aresilient actuator acting on said lever on a line displaced from saidfulcrum, suflicient force on said actuator causing said lever to snapfrom one to the other of said stationary contacts.

13. A snap acting switch including in combination a frame, a U-shapedmember attached to said frame, a torsion member suspended across saidU-shaped member near the ends of the legs of said U-shaped member, saidU-shaped member exerting a tensile force on said torsion member, a leverarm mounted at its center of gravity at the center of said torsionmember, the fulcrum of said lever being established by said torsionmember, stops between said lever and said U-shaped member attached tosaid U-shaped member for restricting other than a twisting movement ofsaid torsion member, movable contacts mounted on opposite sides of thefirst end of said lever, stationary contacts mounted in said frame anddisposed on opposite sides of said first end of said lever to cooperatewith said movable contacts, each of said stationary contacts beingadjustable on said frame, said torsion member biasing said lever to anormal position in engagement with one of said stationary contacts, amagnetic means mounted in said frame in cooperation With a second end ofsaid lever and in spaced relation thereto, said magnetic means beingadjustable on said frame, said second end of said lever acting as anarmature.

References Cited in the file of this patent UNITED STATES PATENTS547,537 Biddle et al Oct. 8, 1895 802,480 Seeley Oct. 24, 1905 1,661,348Grundman Mar. 6, 1928 2,422,861 Skrobisch June 24, 1947 2,452,425Berkholder Oct. 26, 1948 2,614,184 Robinson Oct. 14, 1952 2,641,664Knutson June 9, 1953 FOREIGN PATENTS 404,528 Great Britain Jan. 18, 1934

